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Equation (i) then gives

p = (3-100 + 0-0325X2200 + 474) - 0-23 X 125 - x-6 X 3-2 = 8296-4 cals
Calculating without corrections according to formula (ii),

P = 3'i X (2200 + 474) = 8289-4 cals.

In this way the gross calorific power is found. If the fuel contains 3% of
moisture and 4-504 of hydrogen, 6 (3 + 9 X 4-5) = 261 cals, must be subtracted
from the resulte to obtain the net calorific power, which is therefore 8035-4
(corrected) or 8028-4 (uncorrected).                                                                   ^

(c) HEMPEL'S CALORIMETRIC BOMB. This apparatus, which is simpler
and cheaper than that of Mahler, consists (Fig. 36) of a cylindrical, thick-
walled, cast-iron autoclave A, holding

about 250 c.c. and coated inside with                               S        ^

a thin layer of enamel. It has a screw
lid B, which fits air-tight by means of
an annular lead washer and has an
aperture closable by a conical screw
valve a. The lid carries two rods,
one, b, connected directly with it, and
the other, c, insulated by means of a
rubber coating from the lid, through
which it passes. Each rod terminates
below in a platinum wire bent to a
hook to support a capsule d of refrac-
tory earth, in which is placed the fuel
compressed into cylindrical form in a
mould. Between the two wires is
fitted another very thin platinum wire,
which penetrates into the cylinder of
fuel and ignites the latter when heated
to redness by a current.

The calorimeter is a cylindrical
copper vessel G containing, besides the
bomb, about i litre of water and
placed in a wooden vessel H so that
the distance between the walls is 2 cm.
The whole is then clos'ed by a cover,
through which pass the two terminals,
a thermometer t to read to 0-01 and a stirrer m.

The powdered fuel is pressed into a cylinder weighing about i gram
into which the igniting wire is already pressed. It is weighed exactly and
placed in the dish d and the bomb closed, oxygen being then passed in slowly
until the pressure becomes about 15 atmos. The valve a is then closed
and the bomb placed in a beaker of water to ascertain if it is air-tight;
this being the case, it is dried and arranged in the calorimeter, the stirrer
being put in motion and the thermometer read at intervals of a minute.
After the temperature has remained constant for five minutes, the current
is passed momentarily to cause ignition and the stirring continued and the
periodic reading of the thermometer continued until the temperature passes

FIG. 36~ 0'5  = 0-005,